Process of producing elemental sulphur



March 18, 1930. R. c. BENNER ET AL 1,751,066

PROCESS OF PRODUCING ELEMENTAL SULPHUR Filed Sept. 8, 1926 BY 7 I:

ATTORNEY Patented Mar. 18, 1930 UNITED STATES PATENT" OFFICE RAYMOND C. IBENNEB, OF BAYSIDE, AND ALFRED PAUL THOMIPSON, OF JACKSON HEIGHTS, NEW YORK, ASSIGNOBS TO GENERAL CHEMICAL COMPANY, OF NEW YORK, Y., A CORPORATION OF NEW YORK PROCESS OF PRODUCING ELEMENTAL SULPHUR Application filed September 8,1926. Serial No. 134,160.

This invention relates in general to the production of elemental sulphur and more particularly to the production of elemental sulphur from sulfide ores or from sulphur dioxide and sulfide ores.

In our. co-pending U. S. application No. 91,675, dated March 2, 19:26, we have disclosed and claimed a method for thereductionofsulphur dioxide by means of bituminous coal or coal and oil, whereby elemental sulphur or hydrogen sulfide is produced. In the present application, which comprises a modification of the invention disclosed int-his co-pending application, we disclose a process for the recovery of elemental sulphur from sulfideores by treating a mixture of the sulfide ore, as for example pyritcs or pyrrhotite, and a substantial amount of carbonaceous material such as bituminous coal with a controlled amount of an oxidizing gas. Furthermore, our invention contemplates a process for the reduction of sulphur dioxide by means of a mixture of sulfide ore and carbonaceous fuel wherein the sulphur both from the sulfide ore and the sulphur dioxide is recovered in the elemental form.

The principal objects of our present invention are, first, to' provide an ellicient and economical process for the production of elemental sul hur directly from sulfide ores, wherein substantially complete recovery of all sulphur from the ore is obtained, and sec ondly, to provide a more economical process for the reduction of sulphur dioxide containing gases such as gases from smelters or roasting furnaces, wherein aconsiderableportion of a cheaper and more available fuel than coal, namely sulfide ores, may be employed as a heating and reducing agent.

In the processes heretofore known, for example as described in the patent to Stickney, No. 587,068, it has been proposed to recover elemental sulphur from sulfide ores-b admixing such ores with a small amount not over 5%) of carbonaceous fuel such as coke, and burning such mixture with air in the presence of a large amount of steam. Likewise it has been proposed to treat sulfide ores with steam and reducing gaseous or liquid fuels. Such processes have not provcn fble as methods of producing sulphur because of the large amount of heat required when employing steam and the excessive cost when employing gaseous hydrocarbon fuels. According to our invention we propose to admix with the sulfide ore carbonaceous fuel in amount equal to 10% or more of the total charge, and to employ such carbonaceous fuels as bituminous coal, which comprise substantial amounts of volatile matter preferably 15% or more. Under such conditions we are able to use a comparatively cheap grade of fuel and thereby render our process commercially applicable. When employing our novel process for the reduction of sulphur dioxide, the proportion of carbonaceous fuel will be increased and may even'constitute as much as or even more of the total charge, the balance being sulfide ore. According to this process we are able to produce elemental sulphur from sulphur dioxide at a cost considerably less than heretofore known and further to increase the yield by the sulphur recovered from thesulfide ore.

The accompanying drawing represents diagrammatically one general arrangement of apparatus for carrying out our novel process. The reduction chamber A is provided at the top with an inlet 1 through which a mixture of carbonaceous material, as for example bituminous coal, and a sulfide ore or ores, as for example pyrites, in the granular state, either coarse or finely divided, are continuously introduced into the chamber by a suitable feed mechanism 2. While the particular physical nature of the coal and sul- -fide ore is not of especial importance, nevertheless it should be of such form as will facilitate uniform mixing and' distribution and provide for rapid coking of the coal. At the bottom of the reduction chamber is the inlet 3 whereby an oxidizing gas comprising a por tion of free oxygen is admitted. When the charge is in a state of coarse division the reduction chamber will be substantially filled with the charge. Where, however, the

charge is finely divided, suitable means are provided fordispersing the same rotating cone (not shown} gaseous rea ss a v easier iea will be permitted to drop freely through at least a major portion of the chamber.

When employing our novel process for the reduction of sulphur dioxide, the oxidizing gas introduced at 3 may also contain a considerable proportion of sulphur dioxide, or

encounters a comparatively strong oxidizing atmosphere whereby all the sulphur is removed from the sulfide ore and suflicient heat is developed to maintain the reductlon process. We have found that the temperature of the reduction chamber should be maintained at about 700800 C. or above, for etficient operation.

The reactions which take place in the various parts of the reduction chamber A may be most conveniently described in three parts, each representing a zone in the furnace, By way of example the process will be described as employing pyrites as the sulfide ore and bituminous coal as the carbonaceous fuel. In the top of the chamber, zone a, a reducing atmosphere is maintained and a large part of volatile matter in the coal is driven off with the production of coke. Also the sulfide ore under the influence of heat decomposes to yield free sulphur, according to the equation:

FeS heat- FeS S.

A part of the sulphur thus freed may react with the volatile matter of the coal to yield hydrogen sulfide. Also, the sulphur dioxide arising from the lower zones reacts with the hydrocarbons from the coal and with the hydrogen sulfide produced to yield sulphur vapor, steam, etc.

In the middle zone, zone 6, the atmosphere is maintained substantially neutral or reducing. The coking of the coal is completed and the coke produced here and in zone a is substantially utilized in the reduction of the sulphur dioxide and carbon dioxide ascending from the zone below. The iron sulfide (FeS) resulting from the partial desulphurization of the pyrites serves to reduce a portion of the sulphur dioxide according to the equation:

When a separate inlet is provided for introducing sulphur dioxide containing gases, it should be located approximately at the bottom of this zone 6.

'In the bottom zone, zone 0, the unoxidized iron sulfide descending from zone I; is completely burned owing to'the oxidizing nature of the atmosphere in the zone, to yleld sulphur dioxide and iron oxide. Likewise any carbon remaining in the charge after passing zone I) is burned by the air and sulphur dioxide to carbon dioxide. The sulphur dioxide produced by the oxidation of the sulfide ore in zone 0 passes upwardly and is reduced in zones 72 and a to sulphur and hydrogen sulfide. The amount of air admitted through the inlet- 3 is regulated so that any excess oxygen over that required to oxidize the FeS and carbon is avoided.

The heat developed by the oxidation of the ion sulfide Fe O serves to provide a large portion of the heat required to maintain the temperature of the reduction chamber, thereby reducing the use of the more expensive and less available coal and oil for heating purposes.

In order to provide for an easily regulated amount of reducing gas leaving the reduction chamber we have found it advantageous to provide an inlet 6 at the top of the reduction chamber whereby petroleum oil or other liquid or gaseous hydrocarbon may be introduced. It will be obvious to one skilled in the art that thestrength of the reducing atmosphere might be varied by a variation in the proportion of coal, but the latter is not subject'to such delicate control and the introduction of liquid hydrocarbon permits fine regulation.

As more particularly pointed out in our co-pending application we prefer to employ a carbonaceous reducing agent comprising considerable amounts of volatile hydrocarbons since the presence of such hydrocarbons permits lower temperatures of reduction of the sulphur dioxide and also prevents the formation. of objectionable carbon oxysulfide (COS). Likewise. the presence in the descending charge, of a considerable amount of highly porous coke produced in the upper zone, serves to maintain the charge porous, permitting uniform reaction throughout, and this coke reduces the sulphur dioxide at temperatures below that normally required when using the ordinary metallurgical coke.

lVh'en employing our novel process for the reduction of sulphur dioxide the charge may comprise as much as 50% or more of sulfide ore, the balance being carbonaceous fuel. Certain advantages of such a process will be obvious to one skilled in the art. First, in the regions where sulphur dioxide is produced in large amounts, i. e. in the regions of smelters, pyrites and other sulfide ores are of course present and readily available, whereascoal and oil are often at a premium. Secondly, the process provides a very advantageous way of utilizing the sulphur brasses, sulfide ores containing very considerable amounts of coal, or coals high in iron sulfide, which are at present a drug on the market. Third, elemental sulphur is recovered from the sulfide ores simultaneously with the reduction of the sulphurdioxide, which increases the production of sulphur. Fourth, the objectionable carbon oxysulfide is eliminated from the re.- duction products, due to the employment of g carbonaceous fuel comprising hydrocarons.

WVhen all the sulphur to be recovered in elemental form enters the chamber in the fuel, that is in the form of sulfide ore, the oxidizing gas will be composed chiefly of air or oxygen. In this event it will be obvious that a larger proportion of sulfide ore may be employed for a given amount of coal, since the sulphur dioxide to be reduced by the coal is derived entirely from the ore. The gaseous products of the reduction chamber are removed near the top thereof through the outlet 7 while the ash and cinder may be removed at the bottom of the chamber by suitable means. When the charge is in a state of coarse division, the process is so carried on as to maintain a substantially constant depth of bed of solid fuel, the fuel gradually falling as fresh coal and sulfide ore are added. By a proper regulation of the air, sulphur dioxide, coal and sulfide ore, admitted to the chamber, it is possible to provide for complete oxidation of the coal and ore, maintain the required temperature for the reduction, and reduce substantially all the sulphur dioxide gas to elemental sulphur. I 4

The ash and cinder produced in the process may be eliminated in any of several ways as will be apparent to one skilled in the art. When employing only moderate quantities of sulfide ore, and a comparatively large proportion of coal, the temperature of the reduction process will ordinarily be maintained below that at which the ash and cinder will fuse, and therefore such ash and cinder may be discharged as an unsintered product by such wellknown means as a water seal as shown at 8. When employing larger proportions of sulfide ore, the temperature of the reduction process will ordinarily be maintained somewhat higher, and the ash and cinder will tend to fuse or sinter. Such fused or sintered mass will reach the discharge means in a substantially solid state and may be discharged by the well-known methods applicable thereto, such as, for example, the ram discharge meth od employed in the high temperature gas producers. When, however a very large proportion of sulfide ore is employed it will be found most satisfactory to discharge the ash and cinder in the form of a slag. This may be accomplished by the addition of suitable proportions of lime and silica to the charge and increasing the temperature of the lower zone of the chamber whereby an easily fusible calcium iron silicate is produced Which may betapped ofi. 4 The gaseous products of the reduction chamber comprise considerable sulphur; vapor. However, since the upper zone of the chamber is quite strongly reducing, there will. also be present hydrogen sulfide, hydrocarbons, carbon monoxide, as well as inert nitrogen, some carbon dioxide and any unreduced sulphur dioxide. Practically no carbon oxysulfide is to be found in the exitsince the formation of this objectionable substance is prevented by the considerable amounts of hydrocarbon derived from the bituminous coal and oil.

To provide for the complete interaction of the reducing gases and any sulphur dioxide which may be present, the gas mixture is conducted through conduit 7 to a catalyst chamber B where the gaseous products of the reduction chamber come in contact with a suitable catalyst to aid in the interaction of any unreduced sulfur dioxide with the reducing gases present, namely carbon monoxide, hydrogen sulfide, or hydrocarbons to yield elemental sulphur. When the gas mixture from the reduction chamber contains material amounts of soot or other solid carbonaceous matter," these impurities may be. removed by mechanical separation, or the gases may be passed through a heated checkerwork chamber where the solid particles are burned with carbon dioxide, sulphur dioxide, oxygen, etc. The clean gas is then conducted to the catalyst chamber B.

For regulation of the composition of the gases entering the catalyst chamber wehave provided an inlet 11 in'the conduit 7 through which an oxidizing agent such as sulphur dioxide or air may be admitted. In some cases we prefer to operate the reduction chamber under more strongly reducing conditions so that there will be a considerable quantity of reducing gases such as hydrogen sulfide and carbon monoxide in the gaseous products. In this event, of course, a proportionately large amount of sulphur dioxide or other oxidizing gas will be admitted through the inlet 11. By a proper control of the amount of sulfur dioxide gas or air admitted through the inlet 11 and the amount of oil admitted through the inlet 6, the composition of the gaseous mixture in the catalyst chamber may be adjusted so that there will be present in the mixture interacting proportions of reducing and reducible gases. The reduction of the sulphur dioxide bythe reducing gases will occur according to the following typical equations 2' on. 2so2 co. 211.0 as

QHZS SO2 2HZO 38 ans oz-enz o 2s ber, absorption in oil, etc., or the sulphur mist ma be electrically precipitated.

ny of the known catalysts for aiding the reduction of sulphur dioxide, such as iron oxide, calcium sulfate, calcium sulfide, etc.,

may be. employed in the catalyst chamber.

We have found, however, that particularly good results are obtained when using bauxite, a natural occurring mixture of the oxides of alumina and iron, with minor impurities. Of

the various types of bauxite, that variety commonly known as French bauxite has been found to be particularly useful because of its resistance to disintegration at the temperature employed.

If it is desired to produce hydrogen sulfide by our novel process it will be found necessary to increase the relative amount of bituminous coal or liquid hydrocarbon whereby the reduction of the sulphur dioxide will continue to hydrogen sulfide rather than elemental sulphur. The proper regulation of the reduction chamber whereby hydrogen sulfide will result, will be obvious to one skilled in the art, in view of the foregoing disclosure.

By way of example in disclosing our novel process we have specified the use of pyrites or pyrrhotite as a suitable sulfide ore. However other sulfide ores or concentrates may be used with similar advantage and in fact we have found that any of the sulfide ores of similar type may be suitably employed.

Likewise we have referred to the use of bituminous coal as the preferred type of reducing means. However it will be obvious that other coals and carbonaceous materials may be used, although when employing carbonaceous materials containing small amounts of volatilev hydrocarbon we find it preferable to add oil or other liquid or gaseous hydrocarbon toovercome this deficiency.

Steam may be introduced into the reduce tion chamber when desired, together'with the I air, or through a separate inlet13, to regulate the temperature and to aid in the reduction of the sulfide ore' and sulphur dioxide, but in our referred process no steam is used.

In emp oying the term oxidizing gas throughout the specification and. claims we include'therein such gases as sulphur dioxide which exhibit an oxidizing effect on carbon or. the sulfide ore at thetemperatures employed in our process. We also include withlatter case the entire system is maintained under positive pressure, i. e. of the order of several atmospheres.

Various modifications may be made in our novel process without departing from the spirit thereof and we do not wish to limit the in the appended scope except as defined claims.

We claim:

'1. The process for producing elemental sulphur which comprises contacting a mixture of sulfide ore and carbonaceous material with an oxidizing gas, and passing the gaseous products, while heated, over'a catalyst adapted to complete the interaction of. the

gases to produce elemental sulphur.

2. The process for producing elemental sulphur which comprises contacting a mixture of sulfide ore and a carbonaceous material containing a substantial amount of hy-.

drocarbons with an oxidizing gas and passing the gaseous products in contact with bauxite.

3'. The process for producing elemental sulphur which comprises contacting a mixture of sulfide ore and a carbonaceous material comprising substantial amounts of hydrocarbons with an oxidizing gas comprising substantial amounts of sulphur dioxide, and passing the gaseous products in contact with bauxite. I

4. The process for producing elemental sulphur which comprises contacting a mixture of bituminous coal andf'sulfide ore with an oxidizing gas in counter-current flow so that the'charge is subject first to a reducing atmosphere in which the hydrocarbons of the coal are substantially liberated and the coal is coked and finally to an oxidizing atmosphere, and regulating the proportions of coal to provide at least sufficient reducing means for the reduction of all the sulphur to the elemental form.

5. The process for producing elemental sulphur which comprises continuously introducing a mixture of sulfide ore and coal comprising a substantial amount of hydrocarbons at the top of the reduction chamber whereby the hydrocarbons are substantially liberated and the coal is coked, continuously introducing an oxidizing gas near the bottom of said chamber to flow in counter-current direction to thesolid charge, maintaining an oxidizing atmosphere in the bottom zoneof said chamber, maintaining a reducing atmosphere in the top zone of said chamber, and regulating the proportion of carbonaceousv reducing agent to provide for the elimination of sub-,

itantially all the sulphur in the elemental orm.

6. The process for producing elemental sulphur which comprises contacting a mixtureof sulfide ore and at least 10% carbonaceous material comprising hydrocarbons with an oxidizing gas comprising a substantial amount of sulphur dioxide and regulating the amount of carbonaceous material to provide for substantially complete reduction of all sulphur to the elemental form.

7. The process for producing elemental sulphur which comprises contacting a mixture of sulfide ore and a carbonaceous reducing material comprising hydrocarbons with an oxidizing gas comprising substantial amounts of sulphur dioxide, providing the major portion of the heat required for the reduction process by theoxidation of the sulfide ore, and regulating the amount of carbonaceous reducing material to provide for substantially complete reduction of all the sulphur to the elemental form. 8. The process for producing elemental sulphur which comprises introducing a charge comprising a sulfide ore and at least 10% carbonaceous material comprising hydrocarbons at the top of a reduction chamber, introducing an oxidizing gas comprising substantial amounts of sulphur dioxide near the bottom of the said chamber, maintaining an oxidizing atmosphere in the bottom zone of the said chamber, and maintaining a reducing atmosphere in the top zone of said chamber whereby substantially all the sulphur is reduced to the elemental form.

9. The process for the production of elemental sulphur which comprises contacting a charge comprising a sulfide ore and at least 10% of a carbonaceous reducing agent with an oxidizing gas in counter-current flow, regulating the amount of carbonaceous reducing agent to provide for substantially complete reduction of all sulphur compounds and passing the gaseous products of the reduction process while at a temperature of substantially 350 C. or above in contact'with a catalyst adapted to complete the interaction thereof to produce elemental sulphur.

10. The process for the production of elemental sulphur which comprises contactlng a charge comprising a sulfide ore and at least 10% of a carbonaceous reducing agent w1th an oxidizing gas in counter-current flow, regulating the amount of carbonaceous reduclng agent to provide for substantially complete reduction of all sulphur compounds, regulating the composition of the gaseous products of the reduction process to provide for sub stantially interacting proportions of reducing and reducible gases and passing such gaseous composition while at a temperature of substantially 350 'C. or above in contact with a catalyst adapted to complete the 1nteraction to produce elemental sulphur.

11. The process for the production of elemental sulphur which comprises contactlng a charge comprising a sulfide ore and at least 10% carbonaceous reducin agent with an oxidizing gas comprising su stantial amounts of sulphur dioxide in counter-current flow, regulating the amount of carbonaceous re ducing agent to provide for substantially complete reduction of all sulphur compounds, regulating the composition of the gaseous products of the reduction process by the addition of sulphur dioxide or a reducing gas to provide for substantially interacting proportions of reducing and reducible gases and passing such mixture in contact with a catalyst adapted to complete the interaction to produce elemental sulphur.

12. The process for the production of elemental sulphur which comprises contacting a charge comprising pyrites and at least 10% ofbituminous coal with an oxidizing gas comprising substantial amounts of sulphur dioxide in counter-current flow, maintaining the temperature for the reduction process by the oxidation of the sulfide ore and regulating the amount of coal to provide for substantially complete reduction of all sulphur compounds to yield elemental sulphur.

13. The process for producing elemental sulphur which comprises contacting a mixture of sulfide ore and a carbonaceous ,reducing material comprising hydrocarbons, with an oxidizing gas comprising substantial amounts of sulphur dioxide, maintaining the temperature for the reduction process by the oxidation of the sulfide ore, regulatin the amount of carbonaceous reducing material to provide for substantially complete reduction of all the sulphur to the elemental form, and discharging the ash and cinder in a substantially solid state. k v

14. The process for producing elemental sulphur which comprises dropping a dispersed, finely divided mixture of sulfide ore and carbonaceous fuel through a heated zone and causing an oxidizing gas to flow in counter-current therewith.

15. The process for producing elemental sulphur which comprises dropping a dispersed finely divided mixture of sulfide ore and carbonaceous fuel comprising substantial amounts of hydrocarbons through a heated zone, causing an oxidizing gas to flow in counter-current therewith, and passing the gaseous products while heated above substan tially 350 C. in contact with a catalyst adapted to cause the interaction thereof to produce elemental sulphur.

16. The process of producing elemental sulphur which comprises passing a mixture of sulfide ore and carbonaceous material first through a reducing atmosphere and then through an oxidizing atmosphere, and passing the gaseous products in contact with a catalyst adapted to cause complete interaction of the gases to produce elemental sulhur. P 17. The

sulphur which comprises passing a mixture of pyrites and carbonaceous material first through a reducing atmosphere to substantially extract the volatilizable elemental sulphur, then passing the mixture through an oxidizing atmosphere to substantially extract the remaining sulphur as sulphur dioxide, removing the gaseous products in counter-current relation to the Passage of 10 said mixture, and contacting the gaseous products with a catalyst adapted to complete the interaction to produce elemental sulphur.

In testimony whereof, we aflix our signatures. RAYMOND C. BENNER.

ALFRED RAUL THOMPSON. 

